This project involves investigating the effects of corn malnutrition and protein malnutrition on the functioning of serotonin neurons in brain. Studies deal with the effects of corn malnutrition on pituitary hormone secretion (growth hormone, prolactin). They have also dealt with the effect of corn malnutrition on the uptake into brain of amino acids and metabolic substrates, using the Oldendorf technique. Studies on brain substrate uptake are continuing, as they are indicating interesting results on tryptophan extraction by brain. The effect of corn malnutrition on spinal cord substance P and serotonin is also being investigated as corn rats show increased sensitivity to painful stimuli. These changes in pain threshold may be related to the changes induced by the ingestion of the corn diet in either or both of these compounds in the spinal cord. Finally, we are studying breast milk samples from Guatemala, where corn consumption is high, to determine if free and total tryptophan is selectively reduced. If so, such a result would indirectly suggest a deficiency of tryptophan in other tissues of the body, perhaps also including the brain.